This invention concerns a vertical magnetic recording medium having a laminated structure of a first magnetic film comprising Co--Cr or Co--Cr--W as the main ingredient and a second magnetic film comprising Co--Cr--W--C as the main ingredient, excellent in the vertical magnetic property, and also in the durability, as well as a method of manufacturing the same.
As the magnetic recording system using magnetic tapes, floppy discs, hard discs, etc. a method of longitudinal (in plane) magnetization has generally been employed at present. However, with the increasing requirement for high density recording in recent years, a vertical magnetization system has been considered as a substitute for the conventional system. As the medium for the vertical magnetic recording, those having magnetic films comprising Co--Cr series alloy as the main ingredient have been known.
However, in the case of using a Co--Cr series alloy layer as the recording layer, since it has great frictional resistance with a magnetic head, it is liable to undergo abrasion or injury lacks in durability or lubricancy thus bringing about most important problem for practical use. Further, the Co--Cr film also involves a problem in view of the corrosion resistivity and a film capable of withstanding the use or preservation for a long period of time in high temperature and high humidity circumstance has not yet been obtained. Further, a vertical magnetic recording medium having a Co--Cr--W magnetic film as a sort of Co--Cr series magnetic films has also been known (refer to Japanese Patent Laid-Open Nos. Sho 59-65417, Sho 59-129934 and Sho 57-73913), but such a film also involves the similar problems.
For overcoming such drawbacks, it has been considered to dispose a protection film at the surface of the magnetic film. However, although abrasion resistant material (SiO.sub.2, etc.) or lubricating material (BN, etc.) has been studied for as such protection film, those capable of satisfying the practical demands such as film thickness, excellent abrasion resistance and lubricancy, as well as excellent bondability with the magnetic film have not yet been obtained. Particularly, in the high density recording using the vertical magetic recording, since it is necessary to shorten the distance between the magnetic head and the magnetic film as small as possible, the protection film is restricted to an extremely thin thickness and it has to be excellent in the abrasion resistance.
In order to overcome such problems, it is necessary that the magnetic layer itself has excellent abrasion resistance.
Then, Co--Cr--W--C alloy film has been found as an alloy film excellent in the abrasion resistance and corrosion resistance and it has been confirmed to be prosperous as the vertical magnetic recording film. However, although the Co--Cr--W--C alloy film is extremely excellent in the abrasion resistance and the corrosion resistance, as well as excellent in the vertical magnetic property, it involves problems that the saturation magnetization is somewhat lower as compared with the Co--Cr thin film and the coercive force is somewhat smaller.